International Geology Review

Butakova, Ye. L.

doi: 10.1080/00206816109473586pmid: N/A

Various processes of metasomatism, such as biotitization, aegiritization, and nephelinization, control the ultimate appearance of rocks just as much as magmatic stages of their development. These processes have been brought to light in small composite intrusions in the northern part of the Siberian shield. The aegiritization and nephilinization reconstitute melanocratic rocks with nonalkaline pyroxene into mesocratic rocks with alkaline pyroxene. Of great interest is the conversion of dolerite at the contact with an alkaline intrusion into a rich nepheline rock, which retains vestiges of a poikilophitic texture. The investigation showed that metasomatism is involved in formation of alkaline rocks. Such rocks as carbonates were evidently formed here through the metasomatism of alkaline and nepheline syenite. ---Auth.

Slivko, M. N.

doi: 10.1080/00206816109473587pmid: N/A

The role of manganese in the chemical composition and coloring of tourmaline is discussed. It is shown that manganese tourmaline-tsilaisite is similar to tourmaline-elbaite in composition and condition formation. The miscibility in the sherlite-elbaite-tsilaisite system is complete, but in the sherlite-dravite-tsilaisite system there is a gap between the dravite and tsilaisite, similar to the relationship between dravite and elbaite. Manganese may be present in tourmaline in the form of Mn2+ and Mn3+. The pink coloring of the tourmaline is caused by Mn3+. This conclusion has been drawn from data provided by many authors on the nature of pink coloring of tourmaline, the dyeing properties of Mn2+ and Mn3+, the possibility of the existence of Mn3+ during the crystallization of pink tourmaline, and the distribution of manganese in differently colored tourmaline. --auth.

Amstutz, G. C.

doi: 10.1080/00206816109473588pmid: N/A

Vorobev, G. G.

doi: 10.1080/00206816109473589pmid: N/A

Since their discovery in Czechoslovakia in the 17th century, tektites have been found on all five populated continents. The largest Czech tektites weigh about 100 grams. More than 11 kilograms of samples have been collected from Australia alone. Three principal sources have been postulated: meteoric, lunar, and terrestrial. No theory has yet been generally accepted.-- M. Russell.